Inverter

Abstract

An inverter includes a direct-current conversion unit, a busbar unit, and an inversion unit. The direct-current conversion unit includes a first positive input terminal, a first negative input terminal, a second positive input terminal, a second negative input terminal, a first direct current DC-to-DC module, a second DC-to-DC module, a first on/off control device, a second on/off control device, a first switch, and a second switch. The first positive input terminal and the first negative input terminal are configured to connect a first photovoltaic string, the second positive input terminal and the second negative input terminal are configured to connect a second photovoltaic string, and a connection relationship of a circuit in the direct-current conversion unit can be changed based on combinations of turning-on or turning-off of the first switch and the second switch.

What is claimed is: 
     
       1. An inverter, comprising:
 a busbar unit; 
 an inversion unit having an input terminal connected to the busbar unit, wherein the inversion unit is configured to convert a direct-current (DC) voltage between a positive electrode and a negative electrode of the busbar unit into an alternating current (AC) voltage; 
 a DC conversion unit having a first positive input terminal, a first negative input terminal, a second positive input terminal, a second negative input terminal, a first DC-to-DC module, a second DC-to-DC module, a first on/off control device, a second on/off control device, a first switch, and a second switch, wherein 
 the first positive input terminal is connected to a first terminal of the first DC-to-DC module and one terminal of the first on/off control device, the first negative input terminal is connected to a second terminal of the first DC-to-DC module and the negative electrode of the busbar unit through the first switch, the first negative input terminal is connected to the second positive input terminal through the second switch, and a third terminal of the first DC-to-DC module is connected to another terminal of the first on/off control device and the positive electrode of the busbar unit; 
 the second positive input terminal is connected to a first terminal of the second DC-to-DC module and one terminal of the second on/off control device, the second negative input terminal is connected to a second terminal of the second DC-to-DC module and the negative electrode of the busbar unit, and a third terminal of the second DC-to-DC module is connected to another terminal of the second on/off control device and the positive electrode of the busbar unit; and 
 a controller configured to perform detection on an operating state of the inversion unit, and, when the inversion unit is in the operating state, perform detection on output voltage of a first photovoltaic string and output voltage of a second photovoltaic string, and when detecting that the inversion unit is not operating, control the second switch to be turned off. 
 
     
     
       2. The inverter according to  claim 1 , wherein the first on/off control device is a first diode and the second on/off control device is a second diode,
 one side of the first positive input terminal is connected to the first terminal of the first DC-to-DC module and an anode of the first diode, and the third terminal of the first DC-to-DC module is connected to a cathode of the first diode and the positive electrode of the busbar unit; and 
 one side of the second positive input terminal is connected to the first terminal of the second DC-to-DC module and an anode of the second diode, and the third terminal of the second DC-to-DC module is connected to a cathode of the second diode and the positive electrode of the busbar unit. 
 
     
     
       3. The inverter according to  claim 1 , wherein
 the controller is further configured to: when detecting that the inversion unit is not operating, control the first switch to be turned off or turned on. 
 
     
     
       4. The inverter according to  claim 1 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is less than a first threshold, control the first switch to be turned off, the second switch to be turned on, the first DC-to-DC module to operate, and the second DC-to-DC module not to operate, wherein the first threshold is greater than or equal to voltage required by the busbar unit when the inversion unit is connected to a grid. 
 
     
     
       5. The inverter according to  claim 1 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than or equal to a first threshold and less than a second threshold, control the first switch to be turned off, the second switch to be turned on, and the first DC-to-DC module and the second DC-to-DC module not to operate, and energy input to the inverter is directly input to the busbar unit through the second switch and a first diode. 
 
     
     
       6. The inverter according to  claim 1 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than or equal to a second threshold, the output voltage of the first photovoltaic string is less than a third threshold, and the output voltage of the second photovoltaic string is less than the third threshold, control the first switch to be turned on, the second switch to be turned off, and the first DC-to-DC module and the second DC-to-DC module to operate, wherein the third threshold is greater than or equal to a first threshold and less than the second threshold. 
 
     
     
       7. The inverter according to  claim 1 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than a second threshold, the output voltage of the first photovoltaic string is greater than a third threshold, and the output voltage of the second photovoltaic string is less than the third threshold, control the first switch to be turned on, the second switch to be turned off, the first DC-to-DC module not to operate, and the second DC-to-DC module to operate normally. 
 
     
     
       8. The inverter according to  claim 1 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than or equal to a second threshold, the output voltage of the first photovoltaic string is less than a third threshold, and the output voltage of the second photovoltaic string is greater than the third threshold, control the first switch to be turned on, the second switch to be turned off, the first DC-to-DC module to operate, and the second DC-to-DC module not to operate. 
 
     
     
       9. The inverter according to  claim 1 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than a second threshold, and the output voltage of the first photovoltaic string is greater than a fourth threshold, or the output voltage of the second photovoltaic string is greater than the fourth threshold, control the inversion unit not to operate, and report an alarm, wherein the fourth threshold is a maximum output value of the inverter. 
 
     
     
       10. An inverter, comprising:
 a busbar unit; 
 an inversion unit having an input terminal connected to the busbar unit, wherein the inversion unit is configured to convert direct-current (DC) voltage between a positive electrode and a negative electrode of the busbar unit into an alternating current (AC) voltage; and 
 a DC conversion unit having a first positive input terminal, a first negative input terminal, a second positive input terminal, a second negative input terminal, a first direct current DC-to-DC module, a second DC-to-DC module, a first on/off control device, a second on/off control device, a first switch, and a second switch, wherein 
 the first negative input terminal is connected to a first terminal of the first DC-to-DC module and one terminal of the first on/off control device, the first negative input terminal is further connected to the second positive input terminal through the second switch, an other end of the first positive input terminal is connected to a second terminal of the first DC-to-DC module and the positive electrode of the busbar unit, and a third terminal of the first DC-to-DC module is connected to the negative electrode of the busbar unit and another terminal of the first on/off control device; 
 the second negative input terminal is connected to a first terminal of the second DC-to-DC module and one terminal of the second on/off control device, the second positive input terminal is connected to a second terminal of the second DC-to-DC module and the positive electrode of the busbar unit through the first switch, and a third terminal of the second DC-to-DC module is connected to a negative electrode of the busbar unit and another terminal of the second on/off control device. 
 
     
     
       11. The inverter according to  claim 10 , wherein the first on/off control device is a first diode and the second on/off control device is a second diode,
 the other end of the first negative input terminal is connected to the first terminal of the first DC-to-DC module and a cathode of the first diode, and the third terminal of the first DC-to-DC module is connected to the positive electrode of the busbar unit and an anode of the first diode; and 
 the other end of the second negative input terminal is connected to the first terminal of the second DC-to-DC module and a cathode of the second diode, and the third terminal of the second DC-to-DC module is connected to the negative electrode of the busbar unit and an anode of the second diode. 
 
     
     
       12. The inverter according to  claim 10 , further comprising a controller configured to:
 perform detection on an operating state of the inversion unit, and 
 when the inversion unit is in the operating state, perform detection on an output voltage of a first photovoltaic string and an output voltage of a second photovoltaic string. 
 
     
     
       13. The inverter according to  claim 12 , wherein
 the controller is further configured to: when detecting that the inversion unit is not operating, control the second switch to be turned off and control the first switch to be turned off or turned on. 
 
     
     
       14. The inverter according to  claim 12 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is less than a first threshold, control the first switch to be turned off, the second switch to be turned on, the first DC-to-DC module not to operate, and the second DC-to-DC module to operate, wherein the first threshold is greater than or equal to voltage required by the busbar unit when the inversion unit is connected to a grid. 
 
     
     
       15. The inverter according to  claim 12 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than or equal to a first threshold and less than a second threshold, control the first switch to be turned off, the second switch to be turned on, and the first DC-to-DC module and the second DC-to-DC module not to operate, and energy input to the inverter is directly input to the busbar unit through the second switch and a first diode. 
 
     
     
       16. The inverter according to  claim 12 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than or equal to a second threshold, the output voltage of the first photovoltaic string is less than a third threshold, and the output voltage of the second photovoltaic string is less than the third threshold, control the first switch to be turned on, the second switch to be turned off, and the first DC-to-DC module and the second DC-to-DC module to operate, wherein the third threshold is greater than or equal to a first threshold and less than the second threshold. 
 
     
     
       17. The inverter according to  claim 12 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than a second threshold, the output voltage of the first photovoltaic string is greater than a third threshold, and the output voltage of the second photovoltaic string is less than the third threshold, control the first switch to be turned on, the second switch to be turned off, the first DC-to-DC module not to operate, and the second DC-to-DC module to operate normally. 
 
     
     
       18. The inverter according to  claim 12 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than a second threshold, the output voltage of the first photovoltaic string is less than a third threshold, and the output voltage of the second photovoltaic string is greater than the third threshold, control the first switch to be turned on, the second switch to be turned off, the first DC-to-DC module to operate, and the second DC-to-DC module not to operate. 
 
     
     
       19. The inverter according to  claim 12 , wherein
 the controller is further configured to: when a sum of the output voltage of the first photovoltaic string and the output voltage of the second photovoltaic string is greater than a second threshold, and the output voltage of the first photovoltaic string is greater than a fourth threshold, or the output voltage of the second photovoltaic string is greater than the fourth threshold, control the inversion unit not to operate, and report an alarm, wherein the fourth threshold is a maximum output value of the inverter.